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Physical & Chemical properties

Viscosity

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Description of key information

Viscosity (HEBMP-H): not relevant to solid or aqueous solution

Key value for chemical safety assessment

Additional information

The requirement to test the substance for viscosity was waived in accordance with Section 1 of REACH Annex XI, as this property is not relevant or meaningful for either the solid form or aqueous solution of the substance.

In solution, HEBMP-H (CAS 5995-42-6) undergoes a reversible internal condensation reaction to form a pH-dependent equilibrium mixture with the cyclised structure 4-(Phosphonomethyl)-2-hydroxy-2-oxo-1,4,2-oxaza-phosphorinane (CAS 32422-02-9, c-HEBMP) and water. The precise proportion of the two forms is dependent on pH, temperature and time, and under acidic or neutral conditions, the proportion of c-HEBMP in the multi-constituent substance may reach proportions as high as ≥50% w/w. Spectroscopic evidence from 31P-NMR analysis suggests that in the pH range ca. 1 – 7 a high proportion (50-75% w/w) is present as the cyclised form. The two forms exist in equilibrium therefore it is extremely difficult to separate and purify both forms.